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United States Patent CONTROL MECHANISM FOR STACKER- CONVEYER SYSTEM Stanley M. Mercier, Bexley, Ohio, assignor to The eifrey Manufacturing Company, a corporation of 01110 Application September 18, 1950, Serial No. 185,425 11 Claims. (Cl. 214-) This invention relates particularly to the control apparatus or system for a stacker-conveyer arrangement, and an object of the invention is to provide a control system which is very comprehensive in its coverage, yet extremely flexible and which will control automatically any of the functions of the stacker and/ or associated conveyers.

An object of the invention is toprovide control means to stop the swinging of the boom by its tractor when it is swung through a predetermined angle to either side of its straight-ahead position relative to the head section of the trailing conveyer.

Still another object of the invention is to provide an automatic control operative to start the traction means on the head section of the trailing conveyer so that it will move forward a predetermined amount whenever the dis? charge boom of the system reaches either of its extreme angular positions, the controls also preferably being ar: ranged to cause reverse swinging movement of the discharge boom after the trailing conveyer is moved forward a predetermined amount.

Still another object of the invention is to provide a control system which will control the boom tractor to move it in steps, the stacker preferably being controlled to move a predetermined amount whenever the stack of material which is being discharged reaches a predetermined height.

Other objects of the invention will appear hereinafter, the novel features and combinations being set forth in the appended claims.

' In the accompanying drawings:

Fig. l is a diagrammatic plan view showing one form of stacker-conveyer system or arrangement incorporating features of myinvention;

Fig. 1 is a plan view of the head portion of the head section of the trailing conveyer showing particularly the bull ring connection between said head section of the trailing conveyer and the stacker boom, together with the associated control switches;

Fig. 1 is an elevational view, with parts broken away, of the structure shown in Fig. 1 with some additional portion of the head section of the trailing conveyer also beingshown;

.Figs. 2 to 9 inclusive, go together to make up a wiring diagram of one form of the control system embodying my invention, the complete system being illustrated by turning all the sheets of drawings .sidewise and placing the even numbered drawings, one above the other, in numerical sequence, and the odd numbered drawings, one above the other, in numerical sequence, with the odd numbered drawings on the righthand side. The series starts with Figs. 2 and 3 in lateral alignment;

Fig. 10 is a piping diagram of the hydraulic system provided ,for controlling the head section of the trailing conveyer;

Figs. 2 to 6, inclusive, aresubstitute figures for Figures 2 to 6, inclusive, respectively, and when substituted show a modified control system embodyingfeatures of my invention.

2,734,642 Patented Feb. 14, 1956 ice The conveyer system and certain structural parts thereof Referring first to Fig. 1 of the drawings there is illustrated a stacker-conveyer system incorporating features of my invention which include a stacker 20 having a boom S2 which at its rear end is pivotally connected to the front of the head section of a trailing conveyer or what may be called a mobile conveyer designated S1. The trailing or mobile conveyer S1 is fed by a dump conveyer Di preferably through a feed hopper 21 having the construction disclosed in the application of Gust Weggum, Serial No. 80,695,'filed March 10, 1949, now Patent No. 2,554,077, dated May 22, 1951.

The dump conveyer D1 is preferably fed by a main line conveyer M2 which as illustrated in the drawings is in turn fed by a main line conveyer M1. The general .arrangement of the stacker 20 and the head section of the trailing conveyer as well as a number of the structural features of the trailing conveyer preferably follow the disclosure of my application, Serial No. 145,501, filed February 21, 1950, now Patent No. 2,684,750, dated July 27, 1954, and my application, Serial No. 215,499, filed March 14, 1951, now Patent No. 2,642,984, dated June 23, 1953, which is a division of said application, Serial No. 145,501.

In addition to the structural features disclosed in said application there are certain structural features disclosed in Figs. 1 and 1 of the drawings which are significant in connection with the control system herein claimed. In Figs. 1* and l there is shown the front of the head section of the trailing conveyer S1 including the head pulley 22 and associated conveyer belt 23. As previously mentioned, the rear end of the stacker boom S2 is supported from the front end of the trailing conveyer head section S1 for swinging movement about an upright axis. This is effected by mechanism disclosed in detail in my application, Serial No. 145,501, part of which is also shown in Figs. 1 and 1 This supporting mechanism includes a circular turntable supporting frame 24 having a pair of side brackets 25 by which it is pivotally mounted on the front end of the frame of the conveyer S1 by pivot means 26 which supports the frame 24 for swinging movement on a normally horizontal transversely extending axis. Hydraulic cylinder or jack adjusting means 27 interconnects the rear of the frame 24 and the frame of conveyer S1 for swinging movement of said frame 24 on said transverse axis.

Mounted for rotation relative to the frame 24 in a generally horizontal plane is a bull ring 28 which is provided with spaced rollers, disclosed in more detail in application, Serial No. 145,501, which bull ring is attached to the rear end of the stacker boom S2, as also disclosed more in detail in said application, Serial No. 145,501.

Of significance to the invention of this application is the fact that the bull ring 28 carries a limit switch operating cam 29 which, as illustrated in Fig. l of the drawings, is positioned as it would be with the stacker 20 extending straight forward in longitudinal alignment with the axis of the trailing conveyer section S1. The frame 24 carries a pair of limit switches designated LS9 and LS10, respectively, there being one on each side of said frame 24, as clearly illustrated in Fig. 1 of the drawings. These limit switches LS9 and L810 are adjustably mounted on supporting brackets 30 which constitute part of the frame 24, providing for adjustment of their positions so that they may be actuated by varying angular swinging movement of the boom S2 from its straight-ahead position. The functions performed by the switches LS9 and L810 are described in connection with thewiring diagram.

Wiring diagram-general Figs. 2 to 9, inclusive, of the drawings, when placed as above indicated, disclose the essential portion of the wiring system including features of my invention. In

general three-phase power is supplied for the various motors and single phase power is supplied for the various control relays, solenoids, etc. The three-phase power is provided by means of three power lines L1, L2 and L3 which are connected to a primary source of power through a disconnect switch, as illustrated in Fig. 2 of the drawings. Single phase control voltage is delivered to the various relays, solenoids, etc., by means of parallel bus bars or control lines B1, B2 (Figs. 2, 4, 6 and 8), B3 and B4 (Figs. 3, S, 7 and 9).

To place the stacker-conveyor in operation the first thing that is done is to close the normally open push button start switch 31 seen on Fig. of the drawings. This energizes relay MR over an obvious circuit. Relay MR upon energizing closes the circuit to motor 32 which is energized from lines L1, L2 and L3 through a manual disconnect switch which will, of course, be closed when the unit is in operation. Motor 32 drives the hydraulic pump 33 of the hydraulic system which is disclosed in Fig. of the drawings.

The fourth contact of the relay MR closes an obvious hold-in circuit therefor through normally closed stop switch 34. It also closes a circuit through said normally closed stop switch 34 to the primary of a transformer 35 (see top of Fig. 7) by way of a branch line or conductor 36. The secondary of transformer 35 leads to and thus energizes lines P4 and P8 (Fig. 7). The bottom contacts of the relay MR control circuits which will be described hereinafter.

Upon the energization of lines P4 and P8 (Fig. 7) relay R7 will be immediately energized, providing normally closed switches L829, L530, L833 and L834 are closed. L529 and L830 are the high and low control switches, respectively, in the transverse level control unit mounted on the front transverse bolster of the head section of the trailing conveyer. These switches correspond, for example, to the switches 54 and 55 seen in Fig. 5 of the drawings of my application, Serial No. 124,190, filed October 28, 1949, and now abandoned. They are both normally closed so long as the head section of the trailing conveyer, and consequently the stacker boom S2, are transversely level within the limits of the leveling apparatus.

Switches LS33 and L834 are the high and low switches, respectively, of the leveling device on the turnable 24, such leveling device being shown, for example, at 26 in Fig. 2 of the drawings of my said abandoned application Serial No. 124,190. These switches are normally closed so long as said turntable 24 is level along a plane extending longitudinally of the trailing conveyer head section S1. In other words, if the stacker boom and the turntable, as well as the head section of the trailing conveyer, are level, relay R7 will operate. it not, one of the switches L829, L830, L533 and L534 will be open, in which case relay R7 will not be energized when lines P4 and P8 are energized, in which case a bell or buzzer 37 (see Fig. 7) located in the operators cab will be energized, indicating that one of said switches is open.

Start and control of conveyer belts With relays MR (Fig. 5) and R7 (Fig. 7) closed we are now ready to start the belt of the stacker 20 by energizing the belt driving motor 8 thereof. Relay 523 (Fig. 6) is energized by closing the start switch 38 which closes the circuit through said relay which extends from energized line B2 to energized line B1 as follows: One side of the solenoid or coil of relay S28 is directly connected to line B2. The other side extends over an obvious conductor to switch 38, which is now closed, through normally closed stop switch 39 to conductor 40 which extends through the lower contacts of relay R7 (Fig. 7), then upwardly through the lower contacts of relay MR (Fig. 5). The continuation of the circuit through the lower contacts of relay MR is by conductor 41 (Fig. 5) which extends to Fig. 7 and thence to Fig. 6 through the normally closed contacts of a maintenance switch 42, thence through the normally closed contacts of an emergency stop switch 43 to the line B1. It may be stated that the emergency stop switch 43 is on the belt gangway of the boom S2 so that it can be operated to stop the belt by an operator or repairman who may be working on said gangway. The maintenance switch 42 will remain in whichever position it is thrown, but normally is in the position illustrated in Fig. 6 of the drawings.

It is obvious from the above description that conductors 4i and 41 are effectively connected together when and only when both relays MR (Fig. 5) and R7 (Fig. 7) are energized. Relay S28 on energizing closes a hold-in circuit through its upper contacts which by-passes the start switch 38 but includes the rest of the energizing circuit above described. At its second contacts relay S2S energizes relay S21 (Fig. 6), one side of the said second contacts being connected directly to line B1, the other side extending through a somewhat circuitous path to the coil of relay S21, the other side of said coil extending directly to line B2. The upper contacts of relay S21 provide a hold-in circuit therefor which extends through the second contacts of relay $28 or the second contacts of relay $2M in parallel, one side of each of which contacts is connected with line B1. Relay S21 will therefore be energized whenever relay $28 or relay $2M is energized.

Relay S21 on being energized closes the circuit to motor 8 over its lower contacts, energy from said motor being derived over obvious conductors from the lines L1, L2 and L3 under the control of a disconnect switch. The lower contacts of the relay S2S provide an interlock between this relay which controls motor 8 of the stacker 20 with the driving motor or motors of the conveyor on the head section S1 of the trailing conveyor. The relay 528 may be deenergized and thus stop the motor 8 by opening the normally closed stop switch 39 which would de-energize it and also de-energize relay S21 unless the relay S2M is energized, as now to be described.

In case it is desired to operate the conveyor belt of the boom, or, in other words, to drive the motor 8 without starting the entire system, for example, for maintenance purposes, start switch 44 is closed (Fig. 6) which energizes relay $2M, one side of which is connected directly to line B2, the circuit extending from switch 44 through the normally closed contacts of inc switch 45,'the normally closed contacts of stop switch 46, the normally open contact of maintainence switch 42 which are now closed, and the normally closed contacts of emergency switch 43 to line B1. The upper contacts of relay $2M provide a hold-in circuit which by-passes the start switch 44, the circuit otherwise being the same as above described. The second contacts of relay $2M are in parallel with the second contacts of relay S28 and consequently energize relay S21 in substantially the same way it was energized by said second contacts of relay $28. This will start the motor 8 and maintain it in operation until stop switch 46 is opened to drop out relays 82M and S21.

It is also possible to energize relay S21 momentarily, and thus energize the motor 8 momentarily to inc it along for repair or inspection purposes by controlling said relay S21 direct. This is efiected by closing the normally open contacts 0f inch switch 45 which extends the line 131 through switches 43, now closed but normally open contacts of maintenance switch 42, normally closed stop switch 46, and the lower normally open but now closed contacts of inc switch 45 to one side of the coil of relay S21, the other side beingpermanently and directly connected to line B2. Relay S21 will be energized under these circumstances only so long as the inc switch 45 is held with its lower contacts closed. It is, of course, evident that relay S21 controls motor 8 direct, and motor 8 will always run when relay S21 is energized, providing its disconnect switch is closed and there is power on the lines L1, L2 and L3.

5. As previously mentioned, the lower contacts of relay S2S (Fig. 6) provide an interlock requiring that this relay be energized and thus the belt of the stacker 20 be in operation before the belt 23 of the trailing conveyor can be started. The lower contacts of said relay S25 upon closing energize relay S1S (Fig. 8), one side of which is connected directly to line B2, the other side of which extends through normally closed contacts of a maintenance switch 47 which will stay in any position to which it is adjusted, the circuit extending through the normally closed contacts of emergency stop switch 48 to the line B1. Emergency stop switch 48 is available to an operator or maintenance man on the head section S1.

Relay SIS (Fig. 8) on energizing energizes relay SlA over an obvious circuit through its upper contacts. Relay SIA in turn energizes relay S11 over an obvious cir cuit. Relay S11 upon energizing energizes motors 9 and 10 or either of them alone, assuming their common disconnect switch is closed. If their individual disconnect switches are both closed both motors 9 and 10 will energize. If either of said individual disconnect switches is open, of course, the particular motor disconnected will not be energized. The two motors 9 and 10 are preferably provided for driving the belt 22 as well as variations in the length thereof. In practice one of them has been made a 125 horsepower motor, the other a 30 horsepower motor.

For maintenance purposes the maintenance switch 47 is switched from the position illustrated to one in which its lower contacts are closed. Under these circumstances relay SIM may be energized independently of relay SIS by closing the normally open start switch 49. Relay SlM has a hold-in circuit which by-passes the start switch 49 and extends through its upper contacts. Its lower contacts energize SIA over an obvious circuit. It may be de-energized by opening the normally closed stop switch 50. An inch switch 51 is provided similar in function to the inch switch 45, except, of course, it controls motors 9 and 10, while the inch switch 45 controls motor 8.

When the normally open contacts of inc switch 51 are closed and the maintenance switch is in the maintenance position, relay SIA will be energized over an obvious circuit so long as inch switch 51 is maintained closed, it, like inch switch 45, being the push button type and biased to the positions illustrated in Figs. 6 and 8 of the drawings. Relay SIA when energized energizes relay S11 which controls the motors 9 and/ or 10 as above set forth.

The lower contacts of relay SIS (Fig. 8) provide the I interlock to insure that the motors of the dump conveyer D1 start after the trailing conveyer S1 has been started. Said lower contacts of relay SIS energize relay DIS, one side of which is connected to the line B2, the other side extending through maintenance switch 52 and emergency stop switch 53 to the line B1. The upper contacts of relay DIS on closing energize relay DIA over an obvious circuit, the lower contacts extending the interlock to sub sequent controls, as hereinafter described.

Relay DIA energizes relay DII over an obvious circuit which in turn energizes the motors 13 and/or 14 in a manner obvious from the above description of the operation of motors 9 and 10. Motors 13 and 14 are the driving motors for the dump conveyer D1. In addition to the automatic interlock control of these motors, as above described, they may be operated individually and continuously by reversing the maintenance switch 52 and controlling the relay DIM through its start switch 54 and its normally closed stop switch 55', said relay DIM being provided with upper hold-in contacts which by-pass the start switch 54. The lower contacts of relay DIM energize relay D1A which in turn energizes relay D11 to energize motors I3 and 14.

The inch control for the motors 13 and I4 is provided by inch switch 56 which energizes D1A direct 6 so long as said inc switch 56 is closed and the maintenance switch 52 is in the maintenance position. The maintenance and inch controls for the relays DIA and D11 are substantially the same as those above described for relays SIA and S11.

As above mentioned, the lower contacts of relay DIS (Fig. 3) provides theinterlock with the controls for the motors II and 12 on the main line conveyer M2, said lower contacts controlling conductors 57 and 58 which extend to Fig. 9, the first leading to relay MZS, the other to the normally closed contacts of maintenance switch 59 and then to line B3 through emergency stop switch 60. One side of relay M23 is connected directly to the line B4. At its upper contacts relay M2S energizes relay MZA over an obvious circuit. Relay M2S at its lower contacts provides interlock to the driving motors 15 and 16 of main line conveyer M1, as hereinafter described.

Relay MZA on energizing energizes relay M22 which controls the motors 11 and/or 12 in a manner obvious from the above description of the control of motors 9 and 40, I3 and 14. Maintenance control relay M2M with its hold-in circuit is provided to control relay M2A and relay MZA may be directly controlled through an inch switch, the control being obvious in view of the above description of the operation of maintenance relays SIM and DIM.

The lower contacts of relay M28 upon energizing will energize relay MIS over an obvious circuit which includes the normally closed contacts of maintenance switch 61 and the normally closed contacts of emergency switch 62. Relay MIS on energizing energizes relay MIA over an obvious circuit which in turn energizes relay M11 over an obvious circuit which connects 'Ml conveyer drive motors 15 and/or 16 to the power lines L1, L2 and L3. Relay MIA may be controlled by the maintenance relay Milt I provided with a hold circuit and controlled through the maintenance switch 61 and appropriate start andstop switches in a manner which is obvious in view of the above description of the control for maintenance relays SIM and DIM. Likewise, relay MIA may be controlled direct by an inch switch, the control being obvious in view of the above description of the mode of operation of inch switches 51 and 56.

From the above description it is obvious that the driving motors for the conveyers M1, M2, DI, SI and 20 are all interlocked and during the normal operation they can only be started in the proper sequence, with each leading belt starting before a trailing belt starts. Furthermore, if any leading belt stops, all subsequent belts will stop, while all preceding belts will continue to run. Provision is made, however, in each instance for a maintenance operation of each belt independently of each other belt, but this is only a temporary condition, and the switches are so thrown that during normal operation the interlock is provided. Inching operation is also provided for each. belt; that is, it may be inched or drivenforward' for a short distance only so long as a push button or other switch is maintained closed. This provides great flexibility of operation of the system and one in which during normal working operations the several conveyers, one feeding the other, are interlocked so that in case of any breakdown and stoppage of any belt those belts which feed it will .be automatically stopped while those belts that feed from it will continue to operate and discharge material. This will prevent any building up of material on a belt in case any such belt should-be stopped during operation.

It may be stated that in the interest of simplifying what is inherently a complicated circuit any overload protecting devices and signals which are not essential features or parts of the invention herein claimed have not been illustrated in the wiring diagram.

With the electrical system operated as above described the system will be in that condition wherein all of the belts or conveyers are running and itis ready to receive material any place along the main line conveyer and discharge it over the head or discharge end of the stacker 20. In other words, the conveyer system is in operation and material may be fed to the main line conveyer, such as the main line conveyer M1, in any desired manner.

Level protective circuit As previously described, the limit switches L829, L830, L833, L834 (Fig. 7) are normally closed so long as the head section 81 and the turntable 24 are level. Should either become out of level in either direction and any of said switches open, relay R7 (Fig. 7) will be de-energized which will sound the alarm 37 in the cab and which at its lower contacts will break the hold-in circuit for relay 828 (Fig. 6), thus de-energizing it. Relay 828 on deenergizing will de-energize the entire system and stop all of the conveyer motors since the energization of all of these motors is dependent upon the energization of relay 828. If this condition occurs it will be necessary to level the apparatus so that all of the switches L829,

L830, L833 and L834 (Fig. 7) are closed, whereupon the belts can be started up again only by a manual operation involving the closing of start switch 38 (Fig. 6) which will re-energize relay S28, starting up the conveyer motors in sequence as above described.

. Level control switches and valves actuated thereby As previously described, limit switches L829 and L830 (Fig. 7) are actuated by a leveling instrument on the front bolster of the head section 81. There is another and simi' lar level measuring device mounted thereon, which follows the construction of the divce 26 of my said abandoned application, Serial No. 124,190, which includes a high limit switch L827 (Fig. 7) and a low limit switch L828. Limit switches L827 and L828 are adjusted so that they respond to a lesser tilting of said bolster to actuate them than is required to actuate the corresponding limit switches L829 and L830, respectively.

As also previously described, limit switches L833 and L834 are actuated by a leveling instrument on the turntable 24. There is another and similar level measuring device mounted thereon which also follows the construction of the device 26 of my said abandoned application, Serial No. 124,190, which includes a high limit switch L831 and a low limit switch L832. Limit switches L831 and L832 are adjusted so that they respond to a lesser tilting of said turntable 24 to actuate them than is required to actuate the corresponding limit switches L833 and L834, respectively. In other words, limit switches L827, L828, L831 and L832 are level correcting controlling switches, while limit switches L823, L830, L833 and L834 are level controlled protecting or shut-down limit switches.

If the head section 81 gets out of transverse level enough to close limit switch L827 (Fig. 7) its normally open contacts will be closed and energize relay R1. One side of relay R1 is connected directly to energized line P8, the other side extending, under the conditions indicated, through the closed contacts of limit switch L827, then over an obvious conductor to the upper normally closed contacts of relay R4, then over the upper normally closed contacts of relay R3 to the line P4.

Relay R1 on energizing energizes solenoid 810 over its lower contacts. Solenoid 810 on operating controls a four-way valve 63 (Fig. to expand the left-hand leveling cylinder 64. The left-hand leveling cylinder 64 will correspond with the left-hand cylinder 56 seen in Fig. 3 of my said application, Serial No. 145,501, and left-hand cylinder 56 seen in Fig. 2 of my said application, Serial No. 215,499, now Patent No. 2,642,984. The leveling action will continue until the switch L827 (Fig. 7) is open to de-energize relay R1 and solenoid S10.

If the head section 81 gets out of transverse level in the opposite direction enough to close the normally open contacts of limit switch L828 (Fig. 7), relay R2 will be en 8 ergized over the normally closed upper contacts of relays R3 and R4, the circuit extending from lines P8 to P4. Relay R2 on energizing energizes solenoid 820 through its lower contacts over an obvious circuit. Solenoid 820 (Fig. 10) on being energized expands the right-hand leveling cylinder 64 which corresponds with the right-hand cylinder 56 shown in Fig. 3 of my said application, Serial No. 145,501, to correct the leveling of the head section 81.

The upper normally closed contacts of relays R1 and R2 provide an interlock between these relays and relays R3 and R4 so that neither of the relays R3 or R4 can operate while either relay R1 or R2 is in operation. Likewise, the upper normally closed contacts of relays R3 and R4 provide an interlock with relays R1 and R2 so that if either relay R3 or R4 is operated neither of the relays R1 or R2 can be operated.

if the turntable 24 becomes out of level in a direction sufiicient to operate limit switch L831, relay R3 will be energized over an obvious circuit including the normally closed upper contacts of relays R1 and R2. Upon being energized relay R3 will energize solenoid 83 over its lower contacts. Solenoid 83 upon being energized will actuate a four-way valve (Fig. 10) to expand the hopper leveling cylinder or jack 27 (Fig. 1

If the turntable 24 becomes out of level in the opposite direction an amount sutlicient to close the normally open contacts of limit switch L832, relay R4 will be energized over an obvious circuit including the upper normally closed contacts of relays R1 and R2. Relay R4 on being energized energizes solenoid 84 over its lower contacts. Solenoid 84 on being energized will control the four-way valve 65 (Fig. 10) so as to contract the cylinder or hydraulic jack 27.

As disclosed in detail in said application Serial No. 145,501, the weight of the frame of the head section 81 is carried on the front axle through the two hydraulic jacks designated 56 in said application and 64 in the instant application. Automatic means are provided to ad just the jacks or cylinders 64 so as to maintain the head section frame within a predetermined range of elevation with respect to said front axle. This includes the two limit switches designated 54 in said application, Serial No. 145,501, and best seen in Fig. 9 thereof. These limit switches are designated L835 and L836 in this application and are seen in Fig. 7.

As said main frame reaches such an elevation as to close the normally open contacts of limit switch L835, relay R5 will be energized over an obvious circuit which will energize solenoid 85 over an obvious circuit. Solenoid 85 upon being energized will control a four-way valve 66 (see Fig. 10) to drain hydraulic fluid from the two leveling cylinders 64 and thus lower the frame of the head section 81 until the normally open contacts of limit switch L835 are again opened, de-energizing relay R5 and solenoid S5.

If the said frame 81 is too low relative to the front axle the normally open contacts of limit switch L836 will close, energizing relay R6 over an obvious circuit which includes the normally closed intermediate contacts of relays R1, R3, R2 and R4, thus insuring that relay R6 is only energized when all of said relays R1, R2, R3 and R4 are deenergized. Relay R6 upon ener izing energizes solenoid 86 which will control valve 66 (Fig. 10) to deliver oil under pressure to the two cylinders 64 in parallel which will raise the frame of head section 81 until the normally open contacts of limit switch L836 are again opened.

Attention is now directed particularly to Fig. 10 of the drawings and to the hydraulic circuit which was described in part above and which will now be described in more detail. Said hydraulic circuit includes a pump 33 which supplies hydraulic fluid under relatively high pressure to a pressure or feed line 67, also being provided with a pressure relief valve 68. When the solenoid 810 was operated as above described it functioned to deliver hy' draulic fluid under pressure from the pressure line 67 to acylinder or jack line ,69 which. in one branch includes a check valve 70 preventing flow of hydraulic fluid through the line 69 away from the cylinder 64, but permitting flow of said hydraulic fluid through said line 69 to said cylinder 64.

Thus when solenoid S10 is energized the leveling jack or cylinder 64 will be contracted and hydraulic fluid on the head end thereof will be forced through a line 71 to the head end of the right-hand leveling cylinder 64. Since the line 71 is blocked under these conditions by the valve 66 the hydraulic fluid will necessarily expand the right hand leveling cylinder 64. Fluid from the piston rod side of said right-hand cylinder 64 will flow through a line 72. Since line 72 includes a check valve 73, similar to the check valve 70, this reverse flow of hydraulic fluid cannot flow through it, but it will flow through a bypass pressure relief valve 74. A drain line 75 will drain this reverse flow of hydraulic fluid from the valve 63 to a tank associated with the pump 33.

The check valve 70 has a pressure relief valve 76 bypassing it, the function of which is to permit reverse flow of hydraulic fluid through the line 69 when the solenoid S20 is operated. The line 71 which has parallel branches from the four-way valve 66 leading to the heads of the two leveling cylinders 64 has shut-ofl needle valves 77 therein which are normally open but which may be closed to prevent any seepage of fluid through the valve 66 in case the unit is shut down over-night or the like.

The relief valves 74 and 76 function to prevent wind or the like creating suificient pressure differential between the two leveling cylinders 64 to force the head section S1 out of transverse level. However, they are set so that when hydraulic fluid is delivered to one of the lines 69 or 72 they will open to permit leveling adjustment of the cylinders 64.

If the solenoid S6 is actuated as aforesaid hydraulic fluid from the pressure line 67 will be delivered to the line 71 and expand the jacks or leveling cylinders 64. If solenoid S is energized as aforesaid the line 71 will be connected to the drain line 75 to drain hydraulic fluid from the cylinders 64 and lower the frame S1.

If the solenoid S3 is energized as aforesaid the valve .65 will be controlled to deliver hydraulic fluid to the head end of the cylinder 27 through a pressure operated check valve 78 and a shut-off valve 79. Shut-oft valve 79 may be closed overnight to prevent leakage of fluid past the valve 65 when the pump 33, for example, is idle. Check valve 78 operates to permit free flow of fluid from the pressure or feed line 67 to the head end of the cylinder 27 when solenoid S3 is energized, but normally prevents a reverse flow of fluid therethrough.

If solenoid S4 is energized hydraulic fluid will flow from the pressure line 67 through line 80 to the piston rod end of the cylinder 27. It will also supply pressure over a branch line to the check valve 78 which will open said check valve and permit the reverse flow of fluid from the cylinder 27 through the valve 65 into the drain line 75.

Control of stacker boom swinging crawlers Limit switch LS6 (Fig. 4) is controlled by the angularity between the mast on the tractor boom and the boom frame. It may, for example, follow the disclosure of my application, Serial No. 74,348, filed February 3, 1949, now Patent No. 2,632,558, dated March 24, 1953, and be in the form of the switch 41, 42, 43 or the switch 75.

Limit switches LS3 and LS4 (Fig. 6) are controlled by reverse rectilinear travel of the truck on top of the tractor mast relative to the tractor boom and may correspond, for example, with switches 30 best seen in Fig. 3 of my said application, Serial No. 74,348, now Patent No. 2,632,558.

Limit switch LS9 (Figs. 1 and 2) is operated byextreme right swing of the boom S2, and limit switch LS10 (Figs. 1, 1 and 2) is operated by extreme left swing of the boom S2. Under normal conditions limit switches 10 LS9 and L810 will be closed and relays 7CR and 6 CR energized over an obvious circuit.

Assuming that limit switch LS6 (Fig. 4) is closed (no undesirable tilt of tractor mast present), relay 8CR (Fig. 2) will be energized over an obvious circuit. With limit switches LS3 and LS4 (Fig. 6) closed, relay SCR (Fig. 2) will be energized over an obvious circuit.

Under these normal conditions the system is conditioned for the operation of the two motors 5 and 6 (Fig. 1) which drive the outer and inner crawler, respectively, of the tractor for the stacker 20, which tractor may in general follow the construction of my said application, Serial No. 74,348, now Patent No. 2,632,558, it being understood that each of the crawlers is provided with an individual driving motor.

With relays 8CR and SCR (Fig. 2) energized, the two crawler motors 5 (Figs. 1 and 6) and 6 (Figs. 1 and 5) may be energized as follows: Upon closing the forward push button switch 81 (Fig. 6) relay 5F (Fig. 6) will be energized over the following circuit: from line B2 toone side of the coil of relay 5F, thence through the normally closed intermediate contacts of relay 5R, thence by a conductor 82 across Fig. 4 to Fig. 2 over the now closed third contacts of relay 6CR, thence by a conductor 83 which extends across Fig. 4 to switch 81 which is temporarily closed, thence through stop switch 84 through conductor 85 which extends across Fig. 4 to Fig. 2 and across the now closed lower contacts of relay 8CR, thence along an extension of conductor 85 to the now closed lower contacts of relay SCR to line B1.

Relay 5F (Fig. 6) on energizing energizes relay 55F (Fig. 6) over its lower contacts through an obvious circuit which extends through limit switch LS8 and a normally closed stop switch 86. Limit switch LS8 is operated essentially in the same manner that limit switch LS4 is operated, but it is operated prior to the operation of limit switch LS4, that is, limit switch LS8 is operated by the truck at the top of the boom tractor mast when said truck reaches a predetermined inner position relative to said boom. When this normally closed limit switch LS8 is open it disables relays 55F and 55R and makes it impossible to run motor 5 which drives the outside crawler of the boom tractor (Figs. 1 and 6). Limit switch LS8 will not ordinarily be allowed to open because the truck on top of the tractor mast which supports the boom is provided with a Selsyn transmitter, the recevier of which is placed in the operators cab so as to indicate to the operator at all times the position of said truck relative to the longitudinal axis of said boom. This Selsyn system including a transmitter 87 and a receiver 88, which is of general standard design, is illustrated in Fig. 5 of the drawings.

Relay 5F when energized as above set forth provides a hold-in circuit through its normally open upper contacts which shunt the push button 81. Relay 55F when energized as above set forth closes an obvious circuit to the traction motor 5 for the front crawler of the boom truck, assuming that its disconnect switch is closed. This power circuit which extends to the lines L1, L2 and L3 is clearly illustrated in Fig. 6 of the drawings. To stop the motor 5 the normally closed stop button 84 is opened which de-energizes relay 5F which in turn opens the circuit and de-energizes relay 55F.

If the reverse push button switch 89 (Fig. 6) is closed, relay SR is energized over a circuit which extends from line B2 to the coil of relay 5R, then through the intermediate normally closed contacts of relay 5F, which provides an interlock with this relay, then to conductor 90 which extendsacross Fig. 4 to Fig. 2 and through the now closed third contacts of relay 7R, the circuit continuing by Way of conductor 91 across Fig. 4 to Fig. 6 through the momentarily closed reverse switch 89 .and then to the normally closed stop switch 84 and over the circuit previously-described for'the operation of'relay 5F. Relay 5R closes a hold-in circuit which by-passes the 

